look, its simple, NWFP along with nORTHERN areas wanted to be a part of India. they had a good understanding with Neheru. Balochistan though essetially a Afghan area, was divided by the durand line by UK so that they could hold india, essentially Blaoch provice wanted to either independent or part of Afghan. since the durnad line expired in the last decade, and old desires never died out, thats why they burn. Pak, cant let go of that. thats the only depth they have in geog terms of there country and also is natural resource rich area. otherwise they would afghan, iran too close to karachi, which would have meant sindh also clamouring for nationhood. so baloch is an essential area to keeo pak running and intact. even if they have to burn that province, they would.
